Various analog-to-digital data converters and conversion techniques are available for converting electrical signals from an analog domain to a digital domain. In general, the process of analog-to-digital conversion includes sampling an analog signal and comparing the sampled analog signal to a threshold value. A binary result is recorded depending upon the result of the comparison. The process of comparing the sample to a threshold may be repeated a number of times with each successive comparison using a different threshold and residue of the sample. The number of iterations typically affects the noise level of any result as well as the resolution of the ultimate digital signal.
Sigma-delta analog-to-digital converters employ sigma-delta modulation techniques that digitize an input signal using very low resolution (e.g., one-bit) and a high sampling rate. Oversampling and the use of digital filters increases the resolution to as many as twenty or more bits. Sigma-delta analog-to-digital converters are especially useful for high resolution conversion of low to moderate frequency signals.